1. Field of the Invention
This invention relates to devices and methods useful in electrical distribution systems, and more particularly to a reclosing relay particularly suitable for direct replacement of a variety of existing reclosing relays having different electrical characteristics and connections, and to methods for such replacement.
2. Description of the Prior Art
Reclosing relays are used in substations and feeder lines to automatically reclose a circuit breaker one or more times after it is been tripped by its protective relay. It is been estimated that over 90% of faults occurring on overhead lines are of a temporary nature. For example, a momentary condition caused by a tree limb swaying into a power line in a gust of wind may cause a circuit breaker to open, but the condition that caused the breaker to open will clear as soon as the limb bends back. Such faults may be cleared by momentarily de-energizing the line. Automatic reclosure devices are used in such systems to automatically initiate reclosing impulses to a circuit breaker that has been tripped by its protective relay.
Automatic reclosure devices that are known in the art are basically timing devices. Some of these devices, such as the ACR11 series of mechanical reclosing relays previously manufactured by General Electric Co., included a synchronous motor driving a gear train and a cam shaft with a reset spring through a crown-gear clutch having a magnetic clutch release. These relays contained a series of cam-operated switches, an auxiliary unit, and an interlocking unit. Various designations of non-interchangeable relay types were manufactured by General Electric Co. under this designation, including types ACR11A, ACR11B, ACR11C, ACR11D, ACR11E and ACR11F (hereinafter, ACR11A-ACR11F). All of these models have been discontinued years ago, and are no longer being supplied or maintained by their manufacturer. Thus, they must either be replaced with a unit in inventory or repaired in the event of a failure, or replaced with a newer device that requires substantial rewiring of the case.
Each of the General Electric devices mentioned above (and possibly others from General Electric or other manufacturers) mount in an ACR case. The reclosing relay has two terminal blocks for external connection, one of which is located at the bottom of the unit, and the other one at the top. For at least some models of reclosing relays, the terminal block connections are different from one another. For example, the terminal block connections for the Z coil (an input that is a momentary closure contact that is used to provide an anti-pump function) are at bottom block terminals TB1-7 and TB1-8 in the GE ACR11A device, but are at top block terminals TB2-11 and TB2-17 in the GE ACR11B device. (Terminals are identified as TB1 for the bottom block and TB2 for the top block, with the terminals being numbered from left to right looking from the front.) The differences between these two models are summarized in Tables 1, 2, and 3.
Table 1 shows the terminal connections for the operate coil, reset coil, Z coil (used to provide an anti-pump function), and motor input. Also listed are the reclose, auxiliary, and adjustable auxiliary outputs.
TABLE 1 TERMINAL CONNECTIONS FOR SPECIFIED INPUTS/OUTPUTS Location on Location on Input Output GE ACR11A GE ACR11B Operate Coil -- TB2-11 and TB2-11 and (E set) TB2-12 TB2-12 Reset Coil -- TB1-3 and TB1-3 and (E reset) TB1-4 TB1-4 Z -- TB1-7 and TB2-11 and TB1-8 TB2-17 Motor -- TB1-5 and TB1-6 and TB1-6 TB1-7 -- Reclose TB2-18 TB2-18 -- Auxiliary TB1-1 and TB1-1 and TB1-2 TB1-2 -- Adjustable TB1-9 and TB1-9 and Aux. TB1-10 TB1-10
The wiring internal to the units are also greatly different. Table 2 shows each contact and where it is located. (Contact names may be found in instruction booklet GEH-1786F for reclosing relays GE ACR11B, GE ACR11C, and GE ACR11F, and in instruction booklet GEH-1761 for "Switchgear Reclosing Relay Type ACR11A," both published by General Electric Co.).
TABLE 2 DIFFERENCES IN CONTACT LOCATIONS, GE ACR11A vs. GE ACR11B Location on Location on Input Contact Name GE ACR11A GE ACR11B Operate or E1 TB2-13 and TB2-13 and Reset Coil TB2-14 TB2-14 (E Set or Reset) E2 TB1-3 and TB1-3 and TB1-4 TB1-4 E3 TB1-5 and TB1-5 and TB1-6 TB1-8 E4 TB1-1 and TB1-1 and T1-2 TB1-2 E5 (n/a) TB2-18 and TB2-19 E6 (n/a) TB2-12 and TB2-17 Z Z1 TB2-15 and TB2-14 and TB2-20 TB2-17 Z2 TB2-17 and TB2-12 and TB2-18 TB2-17 Z3 TB2-19 and TB2-17 and TB2-20 TB2-19 Motor AB TB2-17 and TB2-17 and TB2-20 TB2-19 BC TB2-15 and TB2-14 and TB2-20 TB2-17 DE TB1-3 and TB1-3 and TB1-4 TB1-4 GH TB1-5 and TB1-5 and TB1-6 TB1-8 HI (n/a) TB1-8 and TB2-20 JK TB2-15 and TB2-15 and TB2-16 TB2-16 KL TB2-15 and (n/a) TB2-20 MN TB1-3 and TB1-3 and TB1-4 TB1-4 RS TB1-9 and TB1-9 and TB1-10 TB1-10
Finally, another way to distinguish between the GE ACR11A and GE ACR11B is in the location of the reclosing, reset, and motor circuits. Table 3 lists the location of these circuits in these types of reclosing relays.
TABLE 3 LOCATION OF RECLOSING, RESET AND MOTOR CIRCUITS Location on GE Location on GE Circuit ACR11A ACR11B Reclose TB1-1, 2, 7, 8, TB1-1, 2, 9, 10, 9, 10 and TB2-11 and TB2-11 through 20 through 19 Reset TB1-3 and TB1-4 TB1-3 and TB1-4 Motor TB1-5 and TB1-6 TB1-5, 6, 7, 8, and TB2-20
It should be noted that the GE ACR11C, GE ACR11D, GE ACR11E, and GE ACR11F models have the same terminal connections as the GE ACR11B model. Therefore, where a reclosing relay having the terminal connections of the ACR11B is referred to (in this description and the claims), this reference should be understood to mean any of the GE ACR11B, GE ACR11C, GE ACR11D, GE ACR11E, and GE ACR11F model relays. Tables 1, 2, and 3, however, should make it clear to the reader that an ACR customer cannot interchange a relay having terminal connections of the GE ACR11A reclosing relay with one having the terminal connections of an GE ACR11B reclosing relay (and vice versa), but must (at least) specify which of these models is needed when replacing a unit in the field.
However, merely specifying the model type is also not sufficient, as other differences exist between models installed for use in the field. For example, the "B" model attempts a reset 10 seconds after each reclose attempt. The "C" style does not have this ability and will only reset after a full cycle has completed. Thus, if a "B" style has a successful reclose at 20 seconds into a sequence, it will attempt to reset at 30 seconds. The "C" style, by contrast, will wait 185 seconds to attempt a reset. The reset modes are not interchangeable and neither style can be set to function like the other. "B" and "E" style relays also differ in that the "E" style, unlike the "B" style, has a dual rated 115/230 Vac motor. The "F" style also has a dual rated motor, but the "C" style does not.
In addition to the differences highlighted above between models, variations occur even in reclosing relays of the same model, because the motor, reclose, and reset circuits may have been configured to operate on various voltages. A substation using a reclosing relay, for example, always has either 115 or 230 Vac available for the motor. A station battery of 48, 125, or 250 Vdc would also usually be available, in addition to the 115 or 230 Vac sources, for the reclose and reset circuits. This combination of sources suggests a large number of supply voltage configurations for the three circuits is possible. It is not known whether relays have been configured for all possible permutations of supply voltages, but many configurations are certainly being used. In any event, relays are in use where at least two and perhaps even three different supply voltages are used to energize the relay.
Although not all the possible permutations of the General Electric ACR11A-F models may have been produced, it is estimated that it would require at least 100 distinct relays in inventory, plus a large stock of replacement parts, to cover all of the configurations of these relays that are in use, many of which are non-interchangeable with one another. Such a large replacement inventory would be found impractical, especially for a device that is no longer being made or supported by the manufacturer. The estimate of the number of configurations needed may increase if other manufacturer's products, such as those of Westinghouse Electric Co., also have to be supported.
It would therefore be advantageous to provide a method for the field replacement of any of various configurations of installed reclosing relays that does not depend upon having each particular model or configuration of reclosing relay in inventory. It would also be advantageous to provide a device that can be directly retrofit into an installation requiring one of a variety of models and configurations of these prior art reclosing relays without requiring rewiring of the case or the relay. It would further be advantageous if the replacement device did not require a complex motor (such as employed by the General Electric ACR11A-F series devices) with moving parts that wear out, and which therefore require a stock of difficult-to-obtain replacement parts. It would also be advantageous if the replacement device could be made even more reliable through the elimination of unneeded relay contacts. Obviously, it would be yet another advantage if these goals could be realized in a low-cost unit with added functionality.